Alpha adrenoceptors (AAC), beta adrenoceptors (BAC) and dopamine receptors (DR) were characterized in isolated glomeruli (G) and tubules (T) from adult and young rats. Specific binding (SB) was the difference between binding of the ligand alone and in the presence of an excess (100 uM) of a specific competitor. The pairs used were 3H-WB4101 and 1-norepinephrine (AAC), 3H-dihydroalprenolol and 1-propranolol (BAC) and 3H-haloperidol and 1-flupenthixol (DR). SB was rapid, reversible, linear to protein concentration and stereospecific. The potency of agonists and antagonists in competition studies was consistent for the specific receptor being studied. Apparent dissociation constant (Kd) and receptor occupancy (Ro) were calculated from Scatchard plots. DR in glomeruli from 20 day old rats was less compared to adult rats. Tehse studies give the first evidence for specific DR in rat kidney. The presence of specific catecholamine receptors in G may explain the ability of adrenergic and dopaminergic agents to influence glomerular ultrafiltration. These receptors may be involved in the control of glomerular dynamics with maturation. This project summary contained formulas, drawings, tables or nonkeyable data which are not shown above.